Field of the Invention
This invention relates generally to a tool for rotating a rotor on a generator for alignment and maintenance purposes and, more particularly, to a tool for rotating a heavy turbine generator rotor for alignment and maintenance purposes, where the tool includes a hydraulic ratcheting pawl supported in a generator housing that engages notched segments in a plate mounted to a shaft coupling.
Discussion of the Related Art
High voltage generators for generating electricity as a power source are well known in the art. A power plant may be of a nuclear or fossil heat source that rotates a shaft by the expansion of a working gaseous fluid across turbine blades that in turn cause the shaft to rotate. The shaft is coupled to an input shaft of a high voltage generator that is mounted to a rotor having a special configuration of coils. An electrical current provided in the rotor coils generates a magnetic flux around the coils, and as the rotor rotates, the magnetic flux interacts with windings in a stator core enclosing the rotor, which generates a current flow in the windings.
Generators of this and other types require periodic maintenance, where the generator is shut down and various maintenance procedures are performed. For example, it is necessary that the shaft of the turbine be accurately aligned with the shaft of the generator rotor during operation of the machines. Therefore, during maintenance of the generator and turbine this alignment between the two shafts is reset, which may require one or both of the rotor shaft and the turbine shaft to be rotated and oriented relative to each other. Because the rotor is often very large and heavy, for example, 200 tons, properly positioning the rotor requires a specific and safe operation to perform the shaft rotation.
The rotor shaft typically includes an end shaft coupling that includes two coupling halves that are bolted together. During the maintenance operation, the coupling halves are separated, which exposes the bolt holes in each coupling half that are used to secure the coupling halves together. In one known procedure, a machine pin is inserted into one of these holes. A cable is then wrapped around the pin and coupled to an overhead crane hook. By lifting the crane hook, rotary motion can be applied to the rotor. However, there are safety risks associated with this procedure to personnel and equipment. For example, the cable may break if not correctly selected, possibly putting personnel in physical harm. Further, the rotor may continue rolling and once past center with momentum, the cable may be overloaded and break. Also, the crane hook may be overloaded, damaged or require downtime to inspect before continued operation. Further, the pin inserted into a coupling bolt hole may bend and, if overloaded, may damage the coupling bolt hole. In an alternate embodiment, a machine pin is also placed in one of the coupling half holes, a hydraulic ram is set under the pin and pressure is exerted against the pin causing rotor rotation. Access is generally limited and many pinch points are encountered making this method also a safety concern.